Gianna Allegrone

Stereochemistry of the biogeneration of C-10 and C-12 gamma lactones inYarrowia lipolytica andPichia ohmeri

SummaryDegradation of the C-16 and C-18 racemic hydroxy acids 1–4 to C-10 and C-12 γ-lactones 5–8 proceeds inYarrowia lipolytica andPichia ohmeri with opposite stereochemistry

On the mode of baker's yeast reduction of C-7 --- C-10 2-alken-4-olides

Bakers yeast reduction of lactones8,a-d proceeds under kinetic resolution to give (S)11,a-d of low ee values, increasing with the length of the side chain, occurring the double bond saturation in anti fashion on the beta re face, as indicated by the obtainment from4 and6 of5 and7, respectively.

On the steric course of the microbial generation of (Z6)-gamma-dodecenolactone from (10R, S) 10-hydroxy-octadeca-(E8, Z12)-dienoic acid

Summary(Z6)-gamma-dodecenolactone samples produced endogenously inFusariumpoae and biogenerated from (10R, S) 10-hydroxy-octadeca-(E8, Z12)-dienoic acid inCladosporiumsuaveolens show (R) and (S) configurations, respectively.

On the microbial biogeneration of (R) γ-jasmolactone

The biogeneration of (R) Z-7-decen-4-olide (γ-jasmolactone) (6) in Phichia stipitis and ohmeri from one of the products derived from linolenic acid via photooxidation/reduction is reported

Pattern recognition and genetic algorithms for discrimination of orange juices and reduction of significant components from headspace solid‐phase microextraction

INTRODUCTION Orange (Citrus sinensis L.) juice comprises a complex mixture of volatile components that are difficult to identify and quantify. Classification and discrimination of the varieties on the basis of the volatile composition could help to guarantee the quality of a juice and to detect possible adulteration of the product. OBJECTIVE To provide information on the amounts of volatile constituents in fresh-squeezed juices from four orange cultivars and to establish suitable discrimination rules to differentiate orange juices using new chemometric approaches. METHODOLOGY Fresh juices of four orange cultivars were analysed by headspace solid-phase microextraction (HS-SPME) coupled with GC-MS. Principal component analysis, linear discriminant analysis and heuristic methods, such as neural networks, allowed clustering of the data from HS-SPME analysis while genetic algorithms addressed the problem of data reduction. To check the quality of the results the chemometric techniques were also evaluated on a sample. RESULTS Thirty volatile compounds were identified by HS-SPME and GC-MS analyses and their relative amounts calculated. Differences in composition of orange juice volatile components were observed. The chosen orange cultivars could be discriminated using neural networks, genetic relocation algorithms and linear discriminant analysis. Genetic algorithms applied to the data were also able to detect the most significant compounds. CONCLUSIONS SPME is a useful technique to investigate orange juice volatile composition and a flexible chemometric approach is able to correctly separate the juices.

Biogeneration of gamma nonanolide from coriolic acid in Pichia stipitis and Pichia ohmeri

Abstractγ-nonanolide in the (R) enantiomeric form is obtained, close to (R) δ-decanolide, as major transformation product of (R) coriolic acid in Pichia stipitis; feeding experiments of the (S) enantiomer lead to δ-decanolide as major metabolite

Stereochemistry of the conversion of (R) coriolic acid into δ-decanolide in Cladosporium suaveolens

SummaryIn growing cultures of Cladosporium suaveolens (R) coriolic acid (3) is converted into 5-decanolide enriched in the (S) enantiomer (2) (ca. 0.4 ee), while recovered coriolic acid shows the same enantiomeric composition of the precursor, as indicated by NMR studies onto a set of (+)-MTPA derivatives.

Stereochemistry of the methyne–methylene conversion in the biogeneration of (S)-δ-decanolide and (S)-γ-dodecanolide from (13RS)-13-hydroxyoctadeca-9Z,11E-dienoic and (10RS)-10-hydroxyoctadec-8E-enoic acid

In Cladosporium suaveolens the bioconversion of (13RS)-13-hydroxy-[9,10,11,12-2H4]octadeca-9Z,11E-dienoic acid into axially, 2,3,4-trideuteriated (S)-δ-decanolide indicates that protonation of the dienic system occurring at some stage of the degradative sequence takes place on the same face of the molecule. The protonation at position 9 of (10RS)-10-hydroxy-[9,10-2H2]octadeca-8E enoic acid occurring in Yarrowia lipolytica during the biogeneration of (S)-γ-dodecanolide shows the same steric course.

On the enantiomeric composition of biogenerated oct-1-en-3(R)-ol

SummaryThe enantiomeric excess values (ee) of oct-1-en-3(R)-ol samples obtained from linoleic acid by air treatment in the presence of linseed or soybean flour followed by distillation are 0.86 and 0.82, respectively, but 0.32 when the last transformation was performed at pH 6.5; the same material extracted from the mycelium of 15 d old cultures ofNigroporusdurus shows 0.6 ee.